Household Appliance Comprising an Interior Light, and Lighting Subunit Therefor

ABSTRACT

A household appliance comprising a body and a door which surround an interior, and a light source for illuminating the interior. The inventive household appliance further comprises a door opening sensor for detecting the open or closed state of the door and adjusting the mode of operation of the light source based on the detected state of the door. The door opening sensor encompasses a light sensor which is exposed to ambient light when the door is open while being isolated from said ambient light when the door is closed.

The present invention relates to a cupboard- or chest-like household appliance, in particular a refrigeration device provided with interior lighting and a lighting subunit for such a household appliance.

The interior lighting of a refrigeration device such as a refrigerator, upright freezer or a chest freezer is usually controlled by a mechanical switch which is let into the body of the appliance at its open side in such a manner that it is actuated by the opening or closing of the appliance door or flap and in such a manner that a light source in the interior of the appliance is automatically switched on when opening the door and automatically switched off again when closing said door.

The control of the interior lighting by such a mechanical switch has remained almost unchanged for decades and nevertheless, this has a number of disadvantages. Firstly, the mechanical switch is subject to wear but is only accessible with difficulty, in particular when it is recess-mounted between the inner container and the outer wall of the body of the household appliance so that any repair or exchange of this switch is costly. The movement of the door is generally transferred to the switch by means of a slider which can easily get stuck if its guide is contaminated.

Furthermore, the need to attach the switch or at least a slider for its actuation on the open side of the body facing the door whilst the light source is advantageously placed deeper in the interior of the household appliance necessitates a spatial separation of switch and light source so that both must be mounted in separate operations with a correspondingly high labour expenditure.

It is the object of the present invention to provide a household appliance and a lighting subunit for a household appliance which eliminate the aforesaid disadvantages.

The use of a light sensor such as, for example, a photodiode or a phototransistor for adjusting the operating state of the light source for illuminating the interior, as defined in claim 1, allows moving parts to be eliminated completely. Control of the interior lighting is therefore almost free from wear and maintenance.

The light sensor is preferably arranged in the interior of the household appliance in such a manner that it is necessarily cut off from ambient light when the door is closed.

Since such a light sensor is not necessarily cut off from the light produced by the light source itself, a time switch member is appropriately provided for switching off the light source again after a predefined switch-on time. If this time switch member is active when the door is closed, the light sensor receives no more light and the light source remains switched off.

As a result of another embodiment, the light sensor can be arranged in such a manner that it is cut off from light from the light source when the door is closed. In this case, a time switch member is not necessary for switching off the light source again.

A delay member can be provided for delayed switching of the interior lighting after detecting a change in the state of the door so that the user can observe the switching process and ascertain that the interior lighting is not switched on continuously.

The household appliance can also be fitted with an operating mode selector switch which allows a switchover between an automatic control of the light source by the light sensor and at least one further operating mode in which the light source is switched on or off independently of the light detected by the light sensor. This can be desirable if the ambient light in the vicinity of the household appliance is so strong that additional illumination of the interior is not necessary or if the door of the household appliance is opened in the dark and the light sensor does not respond.

Assembly is simplified and costs are therefore saved if the light source and the light sensor are accommodated in a common lighting subunit. Thus, the subject matter of the present invention is also a lighting subunit for a household appliance comprising a light source and a light sensor which is set up to switch on the light source when it detects light.

A time switch member for switching off the light source again after a predefined switch-on time, as explained above, is preferably part of the lighting subunit.

Further features and advantages of the invention are obtained from the following description of the exemplary embodiments with reference to the appended figures. In the figures:

FIG. 1 is a schematic view of a household appliance according to a first embodiment of the invention;

FIG. 2 is a block diagram of the lighting subunit of the household appliance from FIG. 1;

FIG. 3 is a perspective view of a household appliance according to a second embodiment of the invention;

FIG. 4 is a block diagram of a modified embodiment of the lighting subunit; and

FIG. 5 is a block diagram of a further embodiment of the lighting subunit.

FIG. 1 is a perspective view showing a refrigerator as an example of a household appliance according to the invention comprising a body 1, a door 2 hinged to the body 1 and an interior compartment 3. A lighting subunit 4 is located on one side wall of the interior compartment 3. A rear part of the subunit 4 provided with a transparent screen 5 covers a light source; an opaque housing part 6 accommodates a light sensor to which a light guide is connected. The light guide 7 extends along the wall of the interior compartment 3 to an inlet window 8 on the front side of the body 1 which, when the door is closed, is covered in a light-proof fashion by a magnetic sealing profile 9 carried by the door 2. Ambient light can only reach the light sensor when the magnetic sealing profile 9 is lifted from the inlet window 8 on opening the door 2. The light guide 7 is shown by a dashed line in the figure since it is covered by a light-proof adhesive strip 11 on its section extending along the inner wall.

FIG. 2 is a block diagram showing the components of the lighting subunit 4. These comprise a photodiode 12 at which the light guide 7 ends, a capacitor 13 connected in series to the photodiode 12 between two terminals of a DC supply voltage, the light source 14, a transistor 15 connected in series with said light source or an equivalent power switch as well as a resistor 16 which connects a control input of the transistor 15 to a connecting point between photodiode 12 and capacitor 13.

As long as the photodiode 12 is unilluminated and blocked, the capacitor 13 is non-energised and the transistor 15 blocked. The light source 14 is switched off.

If light impinges on the photodiode 12, because the door 2 is opened and the magnetic sealing profile 11 is raised from the inlet window, a photocurrent flowing through the photodiode 12 begins to charge the capacitor 13 so that the voltage at the control input of the transistor 15 gradually increases and this finally opens. The light source 14 is switched on.

If the door 2 is closed again so that no more light impinges upon the photodiode 12, the capacitor 13 discharges via the transistor 15 so that said transistor blocks after a short delay and switches off the light source 14.

FIG. 3 shows a perspective view of a second embodiment of the household appliance. This differs from the embodiment in FIG. 1 in that the photodiode 12 does not receive light via the light guide 7 but through a window 17 that is formed in the opaque housing part 6 at its side facing away from the screen 5 and facing the door opening. If, unlike the diagram in FIG. 3, the lighting subunit 4 is arranged in the immediate vicinity of the closed door 2 so that the door 2, when closed, shields the window 17 from light from the light source 14, the internal structure of the lighting subunit 4 shown in FIG. 2 is also suitable for this embodiment.

The structure shown in FIG. 4 is preferred however, wherein circuit components which have already been explained with reference to FIG. 2 are designated with the same reference numerals. Instead of the resistor 16, a time switch member 18 is switched between the mid point between photodiode 12 and capacitor 13 on the one hand and the control input of the transistor 15 on the other hand. A second transistor 19 is arranged in parallel to the capacitor 13 and its base is connected via a capacitor 21 to the collector of the transistor 15. An operating mode selector switch 20 has three switching positions, a position a in which it connects the emitter of the transistor 15 to earth potential, an unconnected switching position b and a switching position c in which it connects the collector of the transistor 15 to earth.

As long as the refrigerator door 2 is closed and the light source 14 is off, the photodiode 12 thus receives no light, it blocks and the input of the time switch member 18 is at earth potential. Accordingly the output of the time switch member and thus the base of the transistor 15 are also at earth, this blocks and in the position a of the operating mode selector switch 20 shown, the light source 14 thus remains switched off.

When the door is opened so that the photodiode 12 sees light, a photocurrent flows into the capacitor 13 and the voltage at the input of the time switch member 18 increases until this is triggered and delivers a positive potential at its output for a fixedly predefined time interval, as a result of which the transistor 15 becomes transmitting. The light source 14 is thus switched on.

After the predefined time interval has elapsed, the time switch member 18 again delivers earth potential at its output, the transistor 15 returns to the blocking state and the light source 14 is switched off. The potential at the collector of the transistor 15 thus increases abruptly to the value of the supply voltage and a positive voltage pulse reaches the transistor 19 via the capacitor 21 so that said transistor becomes conducting for a short time and short-circuits the capacitor 13. The input signal of the time switch member 18 is thus pulled to earth. After the voltage pulse has decayed, the transistor 19 begins to block again. If the door 2 is still open at this time and ambient light is incident on the photodiode 12, the time switch member 18 is triggered again after a short delay. That is, as long as the door 2 is opened and ambient light is incident on the photodiode 12, the light source 14 operates continuously with short interruptions. These interruptions remind the user that the door 2 should be closed again to avoid unnecessary loss of refrigeration.

If the door 2 is closed again at the time of opening the transistor 19, no more light is incident on the photodiode 12, the capacitor 13 is not charged again and the light source 14 remains switched off.

Similar behaviour can be achieved with the circuit shown in the block diagram in FIG. 5. Here the capacitor 13 is replaced by a resistor 22, a series resistor 23 is inserted between the photodiode and the positive supply potential and the collector of the transistor 19 is not connected to the input of the time switch member 18 but to the mid point between the series resistor 23 and the photodiode 12.

If the door 2 is opened in this embodiment, incidence of light on the photodiode 12 immediately results in a voltage drop at the resistor 22 and thus results in triggering of the time switch member 18 and switching on the light source 14. After the predefined time interval of the time switch member 18 has elapsed, the transistor 13 blocks and the resulting voltage rise at its collector is transferred as a positive pulse to the base of the transistor 19 via the capacitor 21. As a consequence, the transistor 19 short-circuits the photodiode 12 and the resistor 22 so that the potential at the input of the time switch member 18 drops to earth. If the transistor 19 blocks again after charging the capacitor 21, the potential at the input of the time switch member 18 increases again if ambient light continues to be incident on the photodiode 12 and the light source 14 is switched on again. If no more ambient light is present, the light source 14 remains switched off. 

1-9. (canceled)
 10. A cupboard- or chest-like household appliance comprising: a body enclosing an interior compartment; a door being movable between open and closed states with respect to the body for providing access to the interior compartment; a light source for illuminating the interior compartment; a door opening sensor detecting the open or closed state of the door and adjusting the operating state of the light source based on the detected state of the door; and a light sensor being exposed to ambient light when the door is open and being shielded from ambient light when the door is closed.
 11. The household appliance according to claim 10, wherein the light sensor is arranged in the interior compartment.
 12. The household appliance according to claim 11, further comprising a time switch member for switching off the light source again after a predefined switch-on time.
 13. The household appliance according to claim 10, wherein the light sensor is shielded from the light of the light source when the door is closed.
 14. The household appliance according to claim 10, wherein the light sensor comprises a delay member for delayed switching of the light source after detecting a change in state of the door.
 15. The household appliance according to claim 10, further comprising an operating mode selector switch for switching between an automatic control of the light source by the light sensor and at least one further operating mode in which the light source is switched on or off independently of the light detected by the light sensor.
 16. The household appliance according to claim 10, wherein the light source and the light sensor are accommodated in a common lighting subunit.
 17. A lighting subunit for a household appliance comprising: a light source; and a light sensor, the light source being switched on in response to the light sensor detecting light.
 18. The lighting subunit according to claim 17, further comprising a time switch member for switching on the light source again after a predefined switch-on time. 